Techniques for combining a polysiloxane with silica particles are widely practiced and are widely known. The techniques are made for attaining an antifouling effect, an improvement in hardness, a decrease in refractive index, or the like, and are useful in a wide variety of fields.
Incidentally, in a solid imaging element such as a CCD, it has been proposed to form a light condensing microlens on a photoelectric conversion element and to form an anti-reflection film on a surface of the microlens. An anti-reflection film plays a role of preventing noise such as flare or ghost.
Methods of forming an anti-reflection film can be roughly classified into a coating method and a vapor-phase growth method, and among them, the former method is low in cost. In the case of an anti-reflection film formed by vapor-phase growth method, large-scale equipment is generally required, and further it is difficult to form a film having a large area.
An anti-reflection film formed by coating method is generally obtained by a simple step of applying a liquid (coating-type composition) capable of being formed into an anti-reflection film on a substrate and curing the liquid to form a film.
As an anti-reflection film formed by coating method on a lens, there have been proposed an anti-reflection film formed by using a porous layer containing a large number of spaces in the resin (see, for example, Patent Document 1); an anti-reflection film formed by thermal fusion of a low refractive index resin with a lens surface (see, for example, Patent Document 2); an anti-reflection film containing hollow silica and a binder resin (see, for example, Patent Document 3); an anti-reflection film formed by curing a coating solution containing silica sol and a hydrolyzate of alkoxysilane (see, for example, Patent Document 4), and the like.